1. Field of the Invention
The invention is relates to a liquid crystal display (LCD) device, more particularly to a liquid crystal display device having the best performance of contrast ratio and color saturation in the transmissive and reflective areas of color LCD by adjusting the thicknesses of two color filters on the lower and upper transparent substrates.
2. Description of the Prior Art
A color LCD [liquid crystal display] panel comprises two transparent substrates and a liquid crystal layer between the substrates. In general, a color filter is only placed on the transparent substrate opposite to TFTs (thin film transistors). It means that the color filter and TFTs are placed on different transparent substrates respectively opposite to each other.
For the transmissive-type or reflective-type color LCD, the presented color saturation is identical because the distance for light rays passing through a color filter in the whole liquid crystal panel is the same. But for the transflective-type color LCD, please refer to FIG. 1, when external light rays are sufficient to display figures or pictures on the screen, the color LCD will use external light rays 111 as the light source according to the reflection theory. So light rays pass through the color filter 13 twice in the reflective area 11, which will present the higher color saturation. When external light rays are insufficient to display figures or pictures on the screen, the color LCD will use its back light (BL) source according to the transmissive theory. Then the light rays 121 pass through the color filter 13 once in the transmissive area 12, which will present the lower color saturation in comparison to the reflective area 11.
Because of the above reasons, when the transflective-type color LCD uses both of the transmissive and reflective display modes at the same time, the problem of different color saturation is produced. The methods that have been practically used in the industry are illustrated in FIG. 2A and FIG. 2B. A method that the color filter in the reflective area 21 is thinner than the color filter in the transmissive area 22 is adopted. The reflective area 21 is in the left side of FIG. 2A and the transmissive area 22 is in the right side of FIG. 2A. If external light rays 211, as the light source, are sufficient to display figures and pictures on the screen, the light rays 211 of the reflective area 21 will pass through the color filter 212 and be reflected by the reflective electrode on the elevated reflective layer 213. Because of elevated reflective layer 213 with the bumps, many reflective light rays 214 will be produced according to the scattering theory to pass through the liquid crystal layer 23 and the color filter 212 to display figures and pictures on the screen. But when external light rays are insufficient to display figures and pictures on the screen, the LCD will use its BL 221 to pass through the liquid crystal layer 23 and the color filter 222. Owing to the thickness t of color filter 212 be less than the thickness T of color filter 222, it will generate the similar substantially color saturation in both of the reflective and transmissive areas under the thickness compensation theory.
Another method for making many hollow holes in the color filter at the reflective area is adopted in FIG. 2B. The reflective area 26 is in the left side of FIG. 2B and the transmissive area 27 is in the right side of FIG. 2B. When external light rays 261 are sufficient to display figures and pictures on the screen, the LCD will use external light rays 261 as the light source. Therefore, the light rays 261 of the reflective area 26 will pass through the color filter 262 and be reflected by the reflective electrode on the elevated reflective layer 263. Because of elevated reflective layer 263 with the bumps, many reflective light rays 264 will be produced according to the scattering theory to pass through the liquid crystal layer 28 and the color filter 262 to display figures and pictures on the screen. But when external light rays are insufficient, the LCD will use its BL 271, passing through the liquid crystal layer 28 and the color filter 272, to display figures and pictures on the screen. There are many small holes in the color filter 262 and there is not any small hole in the color filter 272. It will generate the similar substantially color saturation in both of the reflective and transmissive areas by using the small holes in the color filter of reflective area.
It still exists the problem for aligning two glass substrates either using the method that the color filter in the reflective area is thinner than the color filter in the transmissive area or the method for making many hollow holes in the color filter at the reflective area. Especially due to the present LCD have quite small pixel; it is very difficult to align the reflective and transmissive areas of two glass substrates. The problem of different color saturation in the reflective and transmissive areas will be produced while there is a little deviation on the alignment.
In the light of the state of the art described above, it is an object of the present invention to provide a liquid crystal display (LCD) device with two color filters on the lower and upper transparent substrates which is immune to the problems of the conventional LCD device described above.
It is another object of this invention to provide a liquid crystal display device with two color filters on the lower and upper transparent substrates to present the same color saturation in the reflective and transmissive areas.
It is a further object of this invention to provide a liquid crystal display device with two color filters on the lower and upper transparent substrates to overcome the problem for disaligning the reflective and transmissive areas on the lower and upper transparent substrates.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a liquid crystal display device which includes a general aspect of the present invention a liquid crystal display device which includes a first substrate having a reflective area and a transmissive area, and a plurality or thin film transistors (TFTs) thereon; a dielectric layer on said first substrate; a first color filter on said dielectric layer; an elevated dielectric layer on said first color filter in said reflective area; a first electrode on said elevated dielectric layer in said reflective area and on said first color filter in said transmissive area, wherein the top surface of said first electrode in said reflective area is higher than the top surface of said first electrode in said transmissive area; a liquid crystal layer on said first electrode; a second electrode on said liquid crystal layer; a second color filter on said second electrode; and a second substrate on said second color filter.
Base on the idea described above, wherein said first and second substrates are transparent.
Base on the aforementioned idea, wherein the material of said dielectric layer is selected from the group consisting of SiO2, Si3N4 and both.
Base on the idea described above, the material of said elevated dielectric layer is photopolymer.
Base on the aforementioned idea, wherein the thickness of said elevated dielectric layer is about 1xcx9c3 xcexcm.
Base on the idea described above, wherein said first and second color filters comprise three non-overlapping color areas.
Base on the aforementioned idea, wherein said three color areas are red, green and blue.
Base on the idea described above, wherein the colors of identical areas on said first and second color filters are same.
Base on the aforementioned idea, wherein said first electrode is coated by using the sputter method.
Base on the idea described above, wherein the height of said first electrode on said elevated dielectric layer is higher than the height of said first electrode on said first color filter in the transmissive areas.
Base on the aforementioned idea, wherein said first electrode is electrically connected with said plurality of TFTs.
Base on the idea described above, wherein the material of said first electrode on said elevated dielectric layer is selected from the group consisting of Al, Ag and AlNd alloy.
Base on the aforementioned idea, wherein the material of said first electrode on said first color filter in the transmissive areas is selected from the group consisting of ITO (indium tin oxide) and IZO (indium zinc oxide).
Base on the idea described above, wherein the best performance in the transmissive and reflective areas can be made by adjusting the thicknesses of two color filters on the lower and upper transparent substrates.
Base on the aforementioned idea, wherein the best performance in the transmissive and reflective areas is the best performance of color saturation in the transmissive and reflective areas.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a liquid crystal display device which includes a first substrate having a reflective area and a transmissive area and a plurality of thin film transistors (TFTs) thereon; a dielectric layer on said first substrate; a first color filter on said dielectric layer in said transmissive area; an elevated dielectric layer on said dielectric layer in said reflective area; a reflective electrode on said elevated dielectric layer; a transmissive electrode on said first color filter, wherein the top surface of said reflective electrode is higher than the top surface of said transmissive electrode, a liquid crystal layer on said reflective electrode and on said transmissive electrode; a common electrode on said liquid crystal layer; a second color filter on said common electrode; and a second substrate on said second color filter.
Base on the idea described above, wherein said first and second substrates are transparent.
Base on the aforementioned idea, wherein the material of said dielectric layer is selected from the group consisting of SiO2, Si3N4 and both.
Base on the idea described above, the material of said elevated dielectric layer is photopolymer.
Base on the aforementioned idea, wherein the thickness of said elevated dielectric layer is about 1xcx9c3 xcexcm.
Base on the idea described above, wherein said first and second color filters comprise three non-overlapping color areas.
Base on the aforementioned idea, wherein said three color areas are red, green and blue.
Base on the idea described above, wherein the colors of identical areas on said first and second color filters are same.
Base on the aforementioned idea, wherein said reflective electrode is coated by using the sputter method.
Base on the idea described above, wherein the material of said reflective electrode on said elevated dielectric layer is selected from the group consisting of Al, Ag and AlNd alloy.
Base on the aforementioned idea, wherein said transmissive electrode is coated by using the sputter method.
Base on the idea described above, wherein the material of said transmissive electrode on said first color filter in the transmissive areas is selected from the group consisting of ITO (indium tin oxide) and IZO (indium zinc oxide).
Base on the aforementioned idea, wherein said transmissive electrode is electrically connected with said reflective electrode.
Base on the idea described above, wherein said transmissive electrode is electrically connected with said plurality of TFTs.
Base on the aforementioned idea, wherein said reflective electrode is electrically connected with said plurality of TFTs.
Base on the idea described above, wherein the best performance in the transmissive and reflective areas can be made by adjusting the thicknesses of two color filters on the lower and upper transparent substrates.
Base on the aforementioned idea, wherein the best performance in the transmissive and reflective areas is the best performance of color saturation in the transmissive and reflective areas.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a liquid crystal display device which includes a first substrate having a reflective area and a transmissive area; a first color filter on said first substrate in said transmissive area; an elevated dielectric layer on said first substrate in said reflective area; a liquid crystal layer on said elevated dielectric layer in said reflective area and on said first color filter in said transmissive area; wherein the height of said liquid crystal layer in said reflective area is smaller than the height of said liquid crystal layer in said transmissive area; a second color filter on said liquid crystal layer; and a second substrate on said second color filter.
Base on the idea described above, wherein said first and second substrates are transparent.
Base on the aforementioned idea, the material of said elevated dielectric layer is photopolymer.
Base on the idea described above, wherein the thickness of said elevated dielectric layer is about 1xcx9c3 xcexcm.
Base on the aforementioned idea, wherein said first and second color filters comprise three non-overlapping color areas.
Base on the idea described above, wherein said three color areas are red, green and blue.
Base on the aforementioned idea, wherein the colors of identical areas on said first and second color filters are same.
Base on the idea described above, wherein the best performance in the transmissive and reflective areas can be made by adjusting the thicknesses of two color filters on the lower and upper transparent substrates.
Base on the aforementioned idea, wherein the best performance in the transmissive and reflective areas is the best performance of color saturation in the transmissive and reflective areas.